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Induction of Beta-galactosidase

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Induction of Beta-galactosidase Aim: This investigation aims to induce and measure the production of the enzyme beta-galactosidase by E. coli. Scientific Background: Cells only express genes when the protein products they code for are needed, thus conserving energy and resources within the cell. The bacteria Escherichia coli (E. coli) can use different carbohydrates as a food source. If lactose, the disaccharide found in milk, is present in the growth medium it must be broken down into the monosaccharide glucose and galactose before it can be utilized as an energy source in respiration. E. coli has a gene for an enzyme called Beta-galactosidase that breaks down the lactose. The presence of the lactose switches on this gene so the enzyme is produced. Beta galactosidase is the enzyme responsible for the first step in the breakdown of lactose. Since beta-galactosidase is a protein, its structure is determined by the information stored in a DNA molecule. There are several steps required to transfer the information stored in a DNA molecule into the structure of a protein. The first is transcription; transcription involves copying the code in a DNA molecule into a messenger RNA molecule. This process occurs in the nucleus of the cell. ...read more.


1cm3 sterile pipettes with filler The use of sterile pipettes makes sure there is no contamination and measures the liquid accurately. 5 or 10cm3 disposable syringe To measure the liquid accurately. Dropper 4 test tubes and rack The test tubes are used to hold each of the four different solutions, and the rack to hold the test tubes securely. Bungs or parafilm for test tubes The bungs ensure that the solutions do not become contaminated. Water bath at 35 �C Disposable gloves Safety Precautions: Aseptic techniques should be employed when using microorganisms so there in no risk of the student becoming infected or cross contamination. Firstly we wore gloves and washed our hands thoroughly. Before we set up the apparatus we made sure the working area was clean by wiping it with disinfectant. The disinfectant used may be toxic or harmful and likely to irritate the skin, so again gloves must be worn. We set up a bunsen burner around our working area so any bacteria in the air will rise and not fall into any of the test tubes. When transferring the E.coli we made sure to use sterile pipettes to avoid cross-contamination. ...read more.


In addition it is important to hold bottles and tubes at an angle to minimize the amount of airborne microbes that can fall into them. However there was still a slight risk of cross contamination. Despite the use of a Bunsen burner bacteria could have still fallen into the test tubes which would have affected my results and made them unreliable. In addition bacteria from overalls and any present on the gloves may have also contaminated the solutions. In addition the amount of time the test tubes were left in the water bath could have affected my results, as if they were not in there for long enough we would not have been able to see the final result. If I was to carry this experiment out again I would measure the colours of the solutions more accurately by using a spectrophotometer or colorimeter to measure the amount of ONP formed in a given time. This would of given more accurate results and I would have been able to plot the numerical data on a graph which would allow easier comparison. Overall I thought my experiment worked quite well as I successfully proved my hypothesis. ?? ?? ?? ?? Tosin Sotubo 12A 1/2/07 ...read more.

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  1. Induction of beta-galactosidase

    * Wash hands before and after experiment. * Always use aseptic techniques to transfer chemicals. Method: 1. Add 5cm� sodium phosphate to four test tubes. 2. Transfer 1cm� E. coli in nutrient broth to the first test tube, and 1cm� E. coli plus nutrient broth (lactose) to the third. 3. Add �-galactosidase to test tube four. 4.

  2. Induction of beta-galactosidase

    Method 1. Wipe down the bench with disinfectant. 2. Label 4 test tubes 1-4. 3. Add 5cm3 sodium phosphate solution to each test tube. 4. Using aseptic techniques, transfer 1cm3 of the E. coli in nutrient broth without lactose to test tube 1.

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